DevTools node tests

In addition to mochitests and xpcshell tests, some panels in DevTools are using node test libraries to run unit tests. For instance, several panels are using Jest to run React component unit tests.

Find the node tests on Try

The DevTools node test task, node(devtools), is running on the Linux 64 opt platform. It is a tier 1 job, which means that any failure will lead to a backout.

Run Tests On Try

To run the DevTools node tests on try, you can use ./mach try fuzzy and look for the job named source-test-node-devtools-tests.

They are also run when using the “devtools” preset: ./mach try --preset devtools.

Node tests try job definition

The definition of those try jobs can be found at taskcluster/kinds/source-test/node.yml.

The definition also contains the list of files that will trigger the node test jobs. Currently the the devtools tests run when any file is modified under devtools/client or devtools/shared.

You will need yarn to be installed in order to run the DevTools tests. See

To run the DevTools tests, the easiest is to rely on the same script as the one used to run the tests on try:

> node devtools/client/bin/devtools-node-test-runner.js --suite={suitename}

At the moment of writing, the supported suites for this script are:

  • aboutdebugging

  • accessibility

  • application

  • compatibility

  • debugger

  • framework

  • netmonitor

  • performance

  • shared_components

  • webconsole

(You can see the full list and the associated configuration in devtools/client/bin/devtools-node-test-runner.js)

Alternatively, you can also locate the package.json corresponding to a given suite, and run yarn && yarn test.

Updating snapshots

Some of the node tests are snapshot tests, which means they compare the output of a given component to a previous text snapshot. They might break if you are legitimately modifying a component and it means the snapshots need to be updated.

A snapshot failure will show up as follows:

› 1 snapshot failed from 1 test suite

It should also mention the command you can run to update the snapshots:

Inspect your code changes or run `yarn run test-ci -u` to update them.

For example, if you need to update snapshots in a specific panel, first locate the package.json corresponding to the node test folder of the panel. In theory it should be under devtools/client/{panelname}/test/node/ but it might be slightly different depending on each panel. Then run yarn run test-ci -u in this folder and add the snapshot changes to your commit.


The “performance” suite performs TypeScript checks. The TypeScript usage in the performance panel is documented at devtools/client/performance-new/ (see rendered version on GitHub).


The devtools-bundle job is a tier2 job which checks if DevTools bundles are outdated. DevTools bundles are generated JavaScript files built from other dependencies in tree in order to run in specific environments (typically a worker).

All the bundles used by DevTools are generated by devtools/client/debugger/bin/bundle.js. The devtools-bundle job is simply running this script and fails if any versioned file is updated.

In order to fix a failure, you should run the script:

> cd devtools/client/debugger/
> yarn && node bin/bundle.js

And commit the changes, either in the commit which updated the bundle dependencies, or in a separate commit in order to keep things separated.